Screening for colorectal cancer remains at relatively low levels, despite its endorsement by expert groups and reimbursement by third- party payers. Little information on the physician and health system factors that may influence use of colorectal cancer screening is available. This study will obtain current, nationally representative data on the physician and health system factors that may influence the use of colorectal cancer screening and diagnostic follow-up in community practice. Study results will be used in the planning and design of intervention and demonstration research aimed at translating the results of controlled trials of screening efficacy into effective community practice. Results also will be used in the planning and design of national surveillance studies to monitor the performance of screening in the planning and design of national surveillance studies to monitor the performance of screening in the community setting. The study has three major components: 1) a nationally representative survey of primary care physicians; 2) a nationally representative survey of specialist physicians who are likely to conduct colorectal cancer screening and/or diagnostic follow up and surveillance procedures; and 3) a nationally representative survey of health plans. A fourth component involves linkage of Medicare claims data to physician survey data for purposes of validating physician self-reports of screening practices and assessing the extent to which the Medicare colorectal cancer screening benefit, effective in January 1998, is being implemented in community practice.